The long term of this proposal is to identify the function of ccmF and ccmH gene products in the biosynthesis of c-type cytochromes in the photosynthetic bacterium Rhodobacter sphaeroides. Specifically, this proposal look forward to answer the following questions: (1) What are the properties of Rhodobacter sphaeroides ccmFH and (2) What are the roles of CcmF and CcmH. Biochemical and genetical approaches will be used to determine if ccmFH are co-transcribe and to generate the respective mutants. Specific cellular location, structure and possible association with other host factors will be achieved by using translational fusions and antibodies against each polypeptide. The specific step where each of these proteins act in c-type cytochromes in strains lacking each proteins. Finally, by using spheroplast and individual proteins required for c-type cytochrome biosynthesis, a CcmF and CcmH functional assay will be desing.